1. Field of the Invention
This invention relates to biodegradable surfactants which may be used as agricultural emulsifiers.
2. Description of the Prior Art
The surface active agent art is quite old and replete with different compositions of useful ionic and nonionic surfactants. An early patent to Schuette et al, U.S. Pat. No. 2,174,761, broadly discloses the preparation of high molecular weight surfactants by the sequential additional of propylene oxide and ethylene oxide to long chain hydrophobic alcohols and specifically discloses the production of surfactants which are solids at room temperature. More recent patents to Lunsted, U.S. Pat. No. 2,674,619 and Jackson et al. U.S. Pat. No. 2,677,700 show surfactant compositions prepared by the addition of propylene oxide and ethylene oxide to a reactive hydrogen compound. Schick discloses the more recent history of nonionic surfactants in his book "Nonionic Surfactants", 1967. Canadian Pat. No. 540,359 describes conjugated polyoxypropylenepolyoxyethylene compounds as surfactants which are prepared by condensing propylene oxide with an alcohol to obtain a polyoxypropylene intermediate polymer and subsequently condensing ethylene oxide with the intermediate polymer to obtain the final product. The Canadian patent requires the use of an alcohol which has a detergency factor of less than 100, i.e., alcohols, if linear, having six or less carbon atoms.
Recent environmental problems have placed particular emphasis on surfactants that are biodegradable. Biodegradability is defined as that property possessed by a material which is capable of being decomposed by bacteria or living organisms, as described for example in the patent to Egan et al, U.S. Pat. No. 3,382,285, while the prior art, as noted above, has disclosed a large number of surfactant products having a wide variety of properties, there has been some difficulty in obtaining surfactants which are effective emulsifiers for agricultural pesticidal solutions, especially those made up a xylene and water, and are also biodegradable.
A recent patent to Scardera and Scott, U.S. Pat. No. 3,956,401 described a low foaming, biodegradable, liquid, non-gelling and nonionic surfactants which has found particular usefulness in automatic dishwashing detergent formulations. However, the surfactants described in that patent have little or no applicability as emulsifiers. An emulsion is usually a dispersion of two mutual insoluble liquids (e.g., water and oil). Emulsifiers or emulsifying agents are used to stabilize the dispersion of these two insoluble liquids. A more complete discussion of emulsions and emulsifying agents can be found in Practical Emulsions, written by H. Bennett, J. C. Bishop, Jr., and M. F. Wulfinghoff and published by Chemical Publishing, Inc., N.Y. (1968), pages 6 to 8.
Now it has been found that the compounds of this invention are nonionic, biodegradable surfactants which are particularly suitable as agricultural emulsifiers, especially in xylene/water solutions.